Field of the Invention
Embodiments relate to methods of operating a communication device which is operable in an active mode and in an idle mode. The invention further relates to a computer program product for executing such a method and to the communication device which is operable in an active mode and in an idle mode.
Background of the Related Art
Modern communication devices such as mobile phones or IP phones (IP: Internet Protocol) are usually connected to a network such as the internet for communication purposes. Most of the time the device may be in an idle mode and only for short periods of time the device is in an active mode. In data communications, an idle mode may be defined as a mode in which no transmissible data are present on a given connection. In particular, during the idle mode, services of the data link layer or link layer (OSI layer 2) are not provided for data exchange. The bit transmission layer or physical layer (OSI layer 1) may be able to transfer data, but the data link layer is neither able to send not to receive instructions or messages. Therefore, a communication instance of the data link layer is unable to operate according to an appointed protocol in the idle mode. Whereas organizational data traffic such as transmission of signaling data may occur, in the idle mode there is no traffic of payload data. An idle mode frequently occurs when at a wired communication device such as an office phone, a handle of the wired communication device is on-hook. In mobile communications, the idle mode may be defined as the mode in which there is no active network connection, a mobile communication device in the idle mode may permanently search for a radio cell suitable to be connected to wherein organizational channels (BCCH, CCCH, CBCH) of the radio cell are permanently received and processed by the mobile communication device. Such data traffic which is required for maintaining the communication device to be able to send and/or receive payload data is not regarded payload data traffic but regarded to be comprised by signaling data traffic. A mobile communication device such as a mobile phone frequently switches into the idle mode when there is no active network connection which is established if a user of the mobile communication device initiates a phone call. An active network connection is also established if an answering machine of a wired or mobile communication device is operating to send and/or receive a message. In the following, the idle mode of a communication device may be defined as the mode in which an established physical layer and an established data link layer of a network are dispensable for data transmission.
In contrast to the idle mode, the active mode may be defined as a mode of a communication device in which an active network connection is established or is necessary to be established. Payload data which a user of the communication device wants to transmit to another communication device of another user is transmitted over the active network connection. Before, during or after the payload transmission, signaling data transmission may occur. For transmitting communication data bidirectionally and in real time, such as speech data and/or video data, high bandwidth network connections are required in the active mode. On the other hand, in the idle mode, when no payload data is to be transferred, a power consumption of the mobile device should be as low as possible. In the following, the active mode of a communication device may be defined as the mode in which an established physical layer and an established data link layer of a network are required for data transmission.
IP phones are often connected via Ethernet. Ethernet is an example of a local area network (LAN) which is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building using network media. The defining characteristics of LANs in contrast to wide area networks (WANs) or global area networks (GANs) include their usually higher data transfer rates, smaller geographic area, and lack of a need for leased telecommunication lines. Usually, a LAN is limited in its extension without further measures of approximately 500 m. The power consumption of the Ethernet itself, meaning the Ethernet connection to a communication device without the communication device, is approximately between 10 and 100 mW. Currently used IP phones are unable to decrease their power consumption significantly under 1000 mW because of the used components and the used hardware design. Therefore, the power consumption of the Ethernet itself is negligible with respect to the power consumption of the communication device connected to the Ethernet.
However, with recent power efficient components such as microcontrollers (MCUs) which are able to operate below approximately 10 mW in low power mode or approximately 100 μA in sleep mode, the power consumption of the Ethernet connection is not negligible any more with respect to the power consumption of the communication device comprising such a microcontroller. A microcontroller or microcontroller unit commonly is a single chip that contains a processor, RAM, ROM (read only memory) clock and I/O (input/output) control unit. A low power mode of a microcontroller may be established for example by switching off external circuits, power budgeting measures, configuring port pins, using high value pool-up resistors, reducing operating voltage, using an external source for CPU (central processing unit) core voltage, and/or using a battery backup for the microcontroller. A sleep mode of a microcontroller also called standby mode is often established in that the microcontroller's high frequency clock oscillator remains running, but the clock tree that drives the CPU circuitry is disabled. In sleep mode, the high-frequency peripheral clock trees are commonly kept alive, allowing autonomous functioning of high-speed peripherals such as a direct memory access (DMA), high-speed serial ports, analog-to-digital and digital-to-analog converters and AES (Advanced Encryption Standard) encryption/decryption. In sleep mode, the RAM (Random Access Memory) remains active and may be accessed by the DMA controller, allowing data retrieved by peripherals to be stored without CPU intervention (CPU: Central Processing Unit). The power consumption of a microcontroller can be lowered even more in the so called deep sleep mode, in which the high frequency MCU oscillator is disabled but the oscillator used to drive critical peripherals is kept running. These may include the real-time clock (RTC) and a watchdog timer as well as a power-on reset and a brown-out detection circuity.
Such advanced MCUs are able to provide a current draw in deep sleep mode of 0.59 μA and still retain full register and RAM contents. For other MCUs the current consumption may range from 10 μA to 30 μA. The time to return to active mode will vary from 2 μs for an optimized design to 8 μs. With such advanced microcontrollers being widely utilized in modern communication devices the power consumption of the network the communication device is connected to, for example the Ethernet according to IEEE 802.3 standard, is not negligible anymore and should be lowered as much as possible for efficient usage of energy. IEEE 802.3 is a working group and a collection of IEEE standards by the working group defining the physical layer and data link layer's media access control (MAC) of wired Ethernet. Physical connections are usually made between nodes and/or infrastructure devices such as hubs, switches, and/or routers by various types of copper or fiber cable. In an effort to reduce the power consumption of Ethernet-LANs the IEEE 802.3az standard has been ratified in September 2010, also called energy-efficient Ethernet or Green Ethernet. This standard is a set of enhancements to the twisted-pair and backplane Ethernet family of computer networking standards that will allow for less power consumption during periods of low data activity.